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Nematicidal Control of Heterodera tabacum. P. M. Miller, Plant Pathologist, Department of Plant Pathology and Botany, The Connecticut Agricultural Experiment Station, New Haven 06504; G. S. Taylor, Plant Pathologist, Department of Plant Pathology and Botany, The Connecticut Agricultural Experiment Station, Windsor 06095. Phytopathology 60:411-414. Accepted for publication 1 October 1969. DOI: 10.1094/Phyto-60-411.

Bay 68138 [ethyl-4-(methylthio)-n-tolyl isopropylphosphoramidate] reduced invasion of roots by larvae of the tobacco cyst nematode, Heterodera tabacum (TCN), but did not kill eggs in cysts. Vorlex (80% 1,3-dichloropropene and 20% methyl isothiocyanate) and Telone (1,3-dichloropropene and related C₃ chlorinated hydrocarbons) killed eggs within cysts; little infection was obtained when cysts were moved from soil treated with Telone or Vorlex into untreated soil. Heterodera tabacum was controlled in the field for only 1 season by a single application of either 60 gal/acre (500 liter/ha) of Telone or 25 gal/acre (209 liter/ha) of Vorlex or by split applications of either 30 gal/acre (250 liter/ha) of Telone or 20 gal/acre (167 liter/ha) of Vorlex. The populations were high again by harvest time. Populations were still low at harvest time after use of 40 lb./acre (40 kg/ha) of 68138. In early summer, Vorlex, Telone, and 68138 controlled TCN larvae 45 cm deep in the soil where populations in untreated soil were already lower than at the soil surface. In greenhouse trials, methomyl (Lannate) [s-methyl N(methylcarbamoyl) oxy] (thioacetimidate) gave good control 3 weeks after addition to soil, but not 8 weeks after addition. Thiabendazole gave excellent control in these greenhouse tests.